Re: suggestions for postgresql setup on Dell 2950 , PERC6i controller

Detailed bonnie++ figures.

http://98.129.214.99/bonnie/report.html



On Wed, Feb 18, 2009 at 1:22 PM, Rajesh Kumar Mallah
<mallah.rajesh@gmail.com> wrote:
> the raid10 voulme was benchmarked again
> taking in consideration above points
>
> # fdisk -l /dev/sda
> Disk /dev/sda: 290.9 GB, 290984034304 bytes
> 255 heads, 63 sectors/track, 35376 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
>
>   Device Boot      Start         End      Blocks   Id  System
> /dev/sda1   *           1          12       96358+  83  Linux
> /dev/sda2              13        1317    10482412+  83  Linux
> /dev/sda3            1318        1578     2096482+  83  Linux
> /dev/sda4            1579       35376   271482435    5  Extended
> /dev/sda5            1579        1839     2096451   82  Linux swap / Solaris
> /dev/sda6            1840        7919    48837568+  83  Linux
> /dev/sda7           29297       35376    48837600   83  Linux
>
>
> CASE                     writes            reads
>                              KB/s               KB/s
>
> ext3(whole disk) 244194 ,  352093               one part whole disk
> xfs(whole disk)   402352  , 547674
>
> 25ext3                 260132 , 420905                 partition only first 25%
> 25xfs                   404291  , 547672                (/dev/sda6)
>
> ext3_25               227307, 348237                  partition
> specifically last  25%
> xfs25                   350661, 474481                  (/dev/sda7)
>
>
> Effect of ReadAhead Settings
> disabled,256(default) , 512,1024
>
> xfs_ra0                 414741 ,   66144
> xfs_ra256            403647,  545026                 all tests on sda6
> xfs_ra512            411357,  564769
> xfs_ra1024          404392,  431168
>
> looks like 512 was the best setting for this controller
>
> Considering these two figures
> xfs25                   350661,   474481                (/dev/sda7)
> 25xfs                   404291  , 547672                (/dev/sda6)
>
> looks like the beginning of the drives are  15% faster
> than the ending sections , considering this is it worth
> creating a special tablespace at the begining of drives
>
> if at all done what kind of data objects  should be placed
> towards begining , WAL , indexes , frequently updated tables
> or sequences ?
>
> regds
> mallah.
>
>>On Tue, Feb 17, 2009 at 9:49 PM, Scott Carey <scott@richrelevance.com> wrote:
>> Generally speaking, you will want to use a partition that is 25% or less the size of the whole disk as well.  If it
is>the whole thing, one file system can place the file you are testing in a very different place on disk and skew
resultsas well. 
>>
>> My own tests, using the first 20% of an array for all, showed that xfs with default settings beat out or equalled
>'tuned'settings with hardware raid 10, and was far faster than ext3 in sequential transfer rate. 
>
> same here.
>
>>
>> If testing STR, you will also want to tune the block device read ahead value (example: /sbin/blockdev -getra
>> /dev/sda6).  This has very large impact on sequential transfer performance (and no impact on random access). >How
largeof an impact depends quite a bit on what kernel you're on since the readahead code has been getting >better over
timeand requires less tuning.  But it still defaults out-of-the-box to more optimal settings for a single >drive than
RAID.
>> For SAS, try 256 or 512 * the number of effective spindles (spindles * 0.5 for raid 10).  For SATA, try 1024 or
>2048* the number of effective spindles.  The value is in blocks (512 bytes).  There is documentation on the >blockdev
command,and here is a little write-up I found with a couple web searches: 
>>http://portal.itauth.com/2007/11/20/howto-linux-double-your-disk-read-performance-single-command
>
>
>>
>> ________________________________________
>> From: pgsql-performance-owner@postgresql.org [pgsql-performance-owner@postgresql.org] On Behalf Of Rajesh Kumar
Mallah[mallah.rajesh@gmail.com] 
>> Sent: Tuesday, February 17, 2009 5:25 AM
>> To: Matthew Wakeling
>> Cc: pgsql-performance@postgresql.org
>> Subject: Re: [PERFORM] suggestions for postgresql setup on Dell 2950 , PERC6i   controller
>>
>> On Tue, Feb 17, 2009 at 5:15 PM, Matthew Wakeling <matthew@flymine.org> wrote:
>>> On Tue, 17 Feb 2009, Rajesh Kumar Mallah wrote:
>>>>
>>>> sda6 --> xfs with default formatting options.
>>>> sda7 --> mkfs.xfs -f  -d sunit=128,swidth=512   /dev/sda7
>>>> sda8 --> ext3 (default)
>>>>
>>>> it looks like mkfs.xfs  options sunit=128 and swidth=512 did not improve
>>>> io throughtput as such in bonnie++ tests .
>>>>
>>>> it looks like ext3 with default options performed worst in my case.
>>>
>>> Of course, doing comparisons using a setup like that (on separate
>>> partitions) will skew the results, because discs' performance differs
>>> depending on the portion of the disc being accessed. You should perform the
>>> different filesystem tests on the same partition one after the other
>>> instead.
>>
>> point noted . will redo the test on ext3.
>>
>>
>>>
>>> Matthew
>>>
>>> --
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>>>
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>>
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>